X-linked Charcot Marie-Tooth Disease (CMTX) is an inherited peripheral neuropathy associated with mutations in the gap junction protein connexins 32 (Cx32). The central tenet of this proposal is that alterations in the functional properties of the ion channel formed by Cx32 can cause CMTX. Further, we propose that to understand the link between mutations and the disorder, we must explore the specific nature of the induced deficits in channel gating, permeability and control of formation. Although an association between a specific mutation in an ion channel and a neuromuscular disease is often compelling, the mechanism that underlies the deficit can remain unrevealed by clinical measures, morphologic examination or epidemiology. The studies )roposed in this grant are a direct and logical continuation of the applicant's previous work exploring the link )etween CMTX and the mutations in the genes controlling gap junction proteins;they build on previous efforts to correlate functional deficits at the cellular and subcellular level with specific mutations and with phenotypic variability. The first two specific aims will use electrophysiologic techniques to examine the loss of Cx32 function resulting from alterations in gating and permeability of mutant forms of Cx32. The third specific aim will again use electrophysiologic techniques to evaluate the possibility that mutations in Cx32 may turn this protein into a suicide channel, leading to disrupted function in cells in which it is expressed. The fourth specific aim utilizes targeted gene replacement to examine the differential effects of two mutant forms of Cx32. The support of a K02 Independent Scientist Award will insure that the applicant is able to maintain at least 75% effort in basic science research while at the same time benefiting from the unique scientific environment of the Department of Neuroscience of the Albert Einstein College of Medicine. These factors will provide an opportunity for continued intellectual and technical development of the PI during this critical early period of development as a physician- scientist engaged in an independent program of translational research.